clear
ARK4_coeffi;
I=eye(6);
B=zeros(6,6);
for j=1:6 
   B(j,:)=b;
end
syms lam_a;
syms lam_d;
% [lam_d,lam_a]=meshgrid(-80:2:0,0,0:1:15);
% for lam_d=-80:0.05:2
% for lam_a=0:0.05:15
R_up=det(I-lam_d.*aI-1i*lam_a.*aE+(lam_d+1i*lam_a).*B);
R_low=det(I-lam_d.*aI-1i*lam_a.*aE);
R=abs(R_up./R_low)-1;
figure(1);
fp1=ezplot(R,[0,15,-80,1]);
view(90,-90);
hold on;
set(gca,'XTick',[0:1:15]);   
set(gca,'yTick',[-80:5:1]); 
axis([0 15 -80 1]);
grid on;
hold on;
title('ARK4');
